An air ejection device for a frictional-resistance reducing ship has been known, which is formed by arranging a plurality of air ejection units on an outer plate of a ship's bottom in a ship width direction (see, for example, Patent Document 1). In this air ejection device for the frictional-resistance reducing ship, a sea chest extending continuously across the ship width direction is provided, which is attached to the inside of the outer plate of the ship's bottom in a manner such that the air ejection units are put in communications.    Patent Document 1: Japanese Patent Application Laid-open No. H11-227675